fsnotify: srcu to protect read side of inode and vfsmount locks
Currently reading the inode->i_fsnotify_marks or
vfsmount->mnt_fsnotify_marks lists are protected by a spinlock on both the
read and the write side. This patch protects the read side of those lists
with a new single srcu.
Signed-off-by: Eric Paris <eparis@redhat.com>
diff --git a/fs/notify/fsnotify.c b/fs/notify/fsnotify.c
index 4788c86..4678b41 100644
--- a/fs/notify/fsnotify.c
+++ b/fs/notify/fsnotify.c
@@ -144,14 +144,15 @@
{
struct fsnotify_mark *mark;
struct hlist_node *node;
+ int idx;
+
+ idx = srcu_read_lock(&fsnotify_mark_srcu);
if (!hlist_empty(&inode->i_fsnotify_marks)) {
- spin_lock(&inode->i_lock);
- hlist_for_each_entry(mark, node, &inode->i_fsnotify_marks, i.i_list) {
+ hlist_for_each_entry_rcu(mark, node, &inode->i_fsnotify_marks, i.i_list) {
if (!(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
mark->ignored_mask = 0;
}
- spin_unlock(&inode->i_lock);
}
if (data_is == FSNOTIFY_EVENT_FILE) {
@@ -159,14 +160,14 @@
mnt = ((struct file *)data)->f_path.mnt;
if (mnt && !hlist_empty(&mnt->mnt_fsnotify_marks)) {
- spin_lock(&mnt->mnt_root->d_lock);
- hlist_for_each_entry(mark, node, &mnt->mnt_fsnotify_marks, m.m_list) {
+ hlist_for_each_entry_rcu(mark, node, &mnt->mnt_fsnotify_marks, m.m_list) {
if (!(mark->flags & FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY))
mark->ignored_mask = 0;
}
- spin_unlock(&mnt->mnt_root->d_lock);
}
}
+
+ srcu_read_unlock(&fsnotify_mark_srcu, idx);
}
static int send_to_group(struct fsnotify_group *group, struct inode *to_tell,
@@ -208,8 +209,10 @@
int fsnotify(struct inode *to_tell, __u32 mask, void *data, int data_is,
const unsigned char *file_name, u32 cookie)
{
+ struct fsnotify_mark *mark;
struct fsnotify_group *group;
struct fsnotify_event *event = NULL;
+ struct hlist_node *node;
struct vfsmount *mnt = NULL;
int idx, ret = 0;
/* global tests shouldn't care about events on child only the specific event */
@@ -237,35 +240,47 @@
!needed_by_vfsmount(test_mask, mnt))
return 0;
- /*
- * SRCU!! the groups list is very very much read only and the path is
- * very hot. The VAST majority of events are not going to need to do
- * anything other than walk the list so it's crazy to pre-allocate.
- */
- idx = srcu_read_lock(&fsnotify_grp_srcu);
+ idx = srcu_read_lock(&fsnotify_mark_srcu);
if (test_mask & to_tell->i_fsnotify_mask) {
- list_for_each_entry_rcu(group, &fsnotify_inode_groups, inode_group_list) {
- if (test_mask & group->mask) {
- ret = send_to_group(group, to_tell, NULL, mask, data, data_is,
- cookie, file_name, &event);
+ hlist_for_each_entry_rcu(mark, node, &to_tell->i_fsnotify_marks, i.i_list) {
+
+ pr_debug("%s: inode_loop: mark=%p mark->mask=%x mark->ignored_mask=%x\n",
+ __func__, mark, mark->mask, mark->ignored_mask);
+
+ if (test_mask & mark->mask & ~mark->ignored_mask) {
+ group = mark->group;
+ if (!group)
+ continue;
+ ret = send_to_group(group, to_tell, NULL, mask,
+ data, data_is, cookie, file_name,
+ &event);
if (ret)
goto out;
}
}
}
- if (needed_by_vfsmount(test_mask, mnt)) {
- list_for_each_entry_rcu(group, &fsnotify_vfsmount_groups, vfsmount_group_list) {
- if (test_mask & group->mask) {
- ret = send_to_group(group, to_tell, mnt, mask, data, data_is,
- cookie, file_name, &event);
+
+ if (mnt && (test_mask & mnt->mnt_fsnotify_mask)) {
+ hlist_for_each_entry_rcu(mark, node, &mnt->mnt_fsnotify_marks, m.m_list) {
+
+ pr_debug("%s: mnt_loop: mark=%p mark->mask=%x mark->ignored_mask=%x\n",
+ __func__, mark, mark->mask, mark->ignored_mask);
+
+ if (test_mask & mark->mask & ~mark->ignored_mask) {
+ group = mark->group;
+ if (!group)
+ continue;
+ ret = send_to_group(group, to_tell, mnt, mask,
+ data, data_is, cookie, file_name,
+ &event);
if (ret)
goto out;
}
}
}
out:
- srcu_read_unlock(&fsnotify_grp_srcu, idx);
+ srcu_read_unlock(&fsnotify_mark_srcu, idx);
/*
* fsnotify_create_event() took a reference so the event can't be cleaned
* up while we are still trying to add it to lists, drop that one.
@@ -279,8 +294,14 @@
static __init int fsnotify_init(void)
{
+ int ret;
+
BUG_ON(hweight32(ALL_FSNOTIFY_EVENTS) != 23);
- return init_srcu_struct(&fsnotify_grp_srcu);
+ ret = init_srcu_struct(&fsnotify_mark_srcu);
+ if (ret)
+ panic("initializing fsnotify_mark_srcu");
+
+ return 0;
}
-subsys_initcall(fsnotify_init);
+core_initcall(fsnotify_init);
diff --git a/fs/notify/fsnotify.h b/fs/notify/fsnotify.h
index 1be54f6..7eed86f 100644
--- a/fs/notify/fsnotify.h
+++ b/fs/notify/fsnotify.h
@@ -6,8 +6,6 @@
#include <linux/srcu.h>
#include <linux/types.h>
-/* protects reads of fsnotify_groups */
-extern struct srcu_struct fsnotify_grp_srcu;
/* all groups which receive inode fsnotify events */
extern struct list_head fsnotify_inode_groups;
/* all groups which receive vfsmount fsnotify events */
@@ -20,6 +18,9 @@
/* destroy all events sitting in this groups notification queue */
extern void fsnotify_flush_notify(struct fsnotify_group *group);
+/* protects reads of inode and vfsmount marks list */
+extern struct srcu_struct fsnotify_mark_srcu;
+
extern void fsnotify_set_inode_mark_mask_locked(struct fsnotify_mark *fsn_mark,
__u32 mask);
/* add a mark to an inode */
diff --git a/fs/notify/group.c b/fs/notify/group.c
index 7ac65ed..48d3a6d 100644
--- a/fs/notify/group.c
+++ b/fs/notify/group.c
@@ -30,8 +30,6 @@
/* protects writes to fsnotify_groups and fsnotify_mask */
static DEFINE_MUTEX(fsnotify_grp_mutex);
-/* protects reads while running the fsnotify_groups list */
-struct srcu_struct fsnotify_grp_srcu;
/* all groups registered to receive inode filesystem notifications */
LIST_HEAD(fsnotify_inode_groups);
/* all groups registered to receive mount point filesystem notifications */
@@ -50,18 +48,17 @@
struct fsnotify_group *group;
__u32 inode_mask = 0;
__u32 vfsmount_mask = 0;
- int idx;
- idx = srcu_read_lock(&fsnotify_grp_srcu);
+ mutex_lock(&fsnotify_grp_mutex);
list_for_each_entry_rcu(group, &fsnotify_inode_groups, inode_group_list)
inode_mask |= group->mask;
list_for_each_entry_rcu(group, &fsnotify_vfsmount_groups, vfsmount_group_list)
vfsmount_mask |= group->mask;
-
- srcu_read_unlock(&fsnotify_grp_srcu, idx);
fsnotify_inode_mask = inode_mask;
fsnotify_vfsmount_mask = vfsmount_mask;
+
+ mutex_unlock(&fsnotify_grp_mutex);
}
/*
@@ -168,6 +165,8 @@
/* clear all inode marks for this group */
fsnotify_clear_marks_by_group(group);
+ synchronize_srcu(&fsnotify_mark_srcu);
+
/* past the point of no return, matches the initial value of 1 */
if (atomic_dec_and_test(&group->num_marks))
fsnotify_final_destroy_group(group);
@@ -216,12 +215,7 @@
*/
__fsnotify_evict_group(group);
- /*
- * now it's off the list, so the only thing we might care about is
- * srcu access....
- */
mutex_unlock(&fsnotify_grp_mutex);
- synchronize_srcu(&fsnotify_grp_srcu);
/* and now it is really dead. _Nothing_ could be seeing it */
fsnotify_recalc_global_mask();
diff --git a/fs/notify/mark.c b/fs/notify/mark.c
index 69c5a16..41f3990 100644
--- a/fs/notify/mark.c
+++ b/fs/notify/mark.c
@@ -85,10 +85,12 @@
#include <linux/fs.h>
#include <linux/init.h>
#include <linux/kernel.h>
+#include <linux/kthread.h>
#include <linux/module.h>
#include <linux/mutex.h>
#include <linux/slab.h>
#include <linux/spinlock.h>
+#include <linux/srcu.h>
#include <linux/writeback.h> /* for inode_lock */
#include <asm/atomic.h>
@@ -96,6 +98,11 @@
#include <linux/fsnotify_backend.h>
#include "fsnotify.h"
+struct srcu_struct fsnotify_mark_srcu;
+static DEFINE_SPINLOCK(destroy_lock);
+static LIST_HEAD(destroy_list);
+static DECLARE_WAIT_QUEUE_HEAD(destroy_waitq);
+
void fsnotify_get_mark(struct fsnotify_mark *mark)
{
atomic_inc(&mark->refcnt);
@@ -144,11 +151,14 @@
list_del_init(&mark->g_list);
- fsnotify_put_mark(mark); /* for i_list and g_list */
-
spin_unlock(&group->mark_lock);
spin_unlock(&mark->lock);
+ spin_lock(&destroy_lock);
+ list_add(&mark->destroy_list, &destroy_list);
+ spin_unlock(&destroy_lock);
+ wake_up(&destroy_waitq);
+
/*
* Some groups like to know that marks are being freed. This is a
* callback to the group function to let it know that this mark
@@ -263,12 +273,17 @@
err:
mark->flags &= ~FSNOTIFY_MARK_FLAG_ALIVE;
list_del_init(&mark->g_list);
+ mark->group = NULL;
atomic_dec(&group->num_marks);
- fsnotify_put_mark(mark);
spin_unlock(&group->mark_lock);
spin_unlock(&mark->lock);
+ spin_lock(&destroy_lock);
+ list_add(&mark->destroy_list, &destroy_list);
+ spin_unlock(&destroy_lock);
+ wake_up(&destroy_waitq);
+
return ret;
}
@@ -326,3 +341,42 @@
atomic_set(&mark->refcnt, 1);
mark->free_mark = free_mark;
}
+
+static int fsnotify_mark_destroy(void *ignored)
+{
+ struct fsnotify_mark *mark, *next;
+ LIST_HEAD(private_destroy_list);
+
+ for (;;) {
+ spin_lock(&destroy_lock);
+ list_for_each_entry_safe(mark, next, &destroy_list, destroy_list) {
+ list_del(&mark->destroy_list);
+ list_add(&mark->destroy_list, &private_destroy_list);
+ }
+ spin_unlock(&destroy_lock);
+
+ synchronize_srcu(&fsnotify_mark_srcu);
+
+ list_for_each_entry_safe(mark, next, &private_destroy_list, destroy_list) {
+ list_del_init(&mark->destroy_list);
+ fsnotify_put_mark(mark);
+ }
+
+ wait_event_interruptible(destroy_waitq, !list_empty(&destroy_list));
+ }
+
+ return 0;
+}
+
+static int __init fsnotify_mark_init(void)
+{
+ struct task_struct *thread;
+
+ thread = kthread_run(fsnotify_mark_destroy, NULL,
+ "fsnotify_mark");
+ if (IS_ERR(thread))
+ panic("unable to start fsnotify mark destruction thread.");
+
+ return 0;
+}
+device_initcall(fsnotify_mark_init);
diff --git a/include/linux/fsnotify_backend.h b/include/linux/fsnotify_backend.h
index 8e24cdf..8415939 100644
--- a/include/linux/fsnotify_backend.h
+++ b/include/linux/fsnotify_backend.h
@@ -302,6 +302,7 @@
#define FSNOTIFY_MARK_FLAG_IGNORED_SURV_MODIFY 0x08
#define FSNOTIFY_MARK_FLAG_ALIVE 0x10
unsigned int flags; /* vfsmount or inode mark? */
+ struct list_head destroy_list;
void (*free_mark)(struct fsnotify_mark *mark); /* called on final put+free */
};